class Goods:
    def __init__(self):
        self.size='25'


    def sale(self):
        print('商品正在售卖')

    def kind(self):
        print('商品类')



class Pen(Goods):
    def __init__(self):
        pass


    def sale(self):
        print('笔正在售卖')

    def kind(self):
        print('笔类')

pen=Pen()
pen.sale()
pen.kind()
print(pen)